The present invention generally relates to removable storage devices for electronic information. More particular, the present invention provides a technique including an apparatus and methods for the movement and operation of a storage device including a magnetic head used to read and write data into a removable disk.
Consumer electronics including television sets, personal computers, and stereo or audio systems, have changed dramatically since their availability. Television was originally used as a stand alone unit in the early 1900""s, but has now been integrated with audio equipment to provide video with high quality sound in stereo. For instance, a television set can have a high quality display coupled to an audio system with stereo or even xe2x80x9csurround soundxe2x80x9d or the like. This integration of television and audio equipment provides a user with a high quality video display for an action movie such as STARWARS(trademark) with xe2x80x9clife-likexe2x80x9d sound from the high quality stereo or surround sound system. Accordingly, the clash between Luke Skywalker and Darth Vader can now be seen as well as heard in surround sound on your own home entertainment center. In the mid-1990""s, computer-like functions became available on a conventional television set. Companies such as WebTV of California provide what is commonly termed as xe2x80x9cInternetxe2x80x9d access to a television set. The Internet is a world wide network of computers, which can now be accessed through a conventional television set at a user location. Numerous displays or xe2x80x9cwet sitesxe2x80x9d exist on the Internet for viewing and even ordering goods and services at the convenience of home, where the act of indexing through websites is known as xe2x80x9csurfingxe2x80x9d the web. Accordingly, users of WebTV can surf the Internet or web using a home entertainment center.
As merely an example, FIG. 1 illustrates a conventional audio and video configuration, commonly termed a home entertainment system, which can have Internet access. FIG. 1 is generally a typical home entertainment system, which includes a video display 10 (e.g., television set), an audio output 20, an audio processor 30, a video display processor 40, and a plurality of audio or video data sources 50. Consumers have often been eager to store and play back pre-recorded audio (e.g., songs, music) or video using a home entertainment system. Most recently, consumers would like to also store and retrieve information, commonly termed computer data, downloaded from the Internet.
Music or audio have been traditionally recorded on many types of systems using different types of media to provide audio signals to home entertainment systems. For example, these audio systems include a reel to reel system 140, using magnetic recording tape, an eight track player 120, which uses eight track tapes, a phonograph 130, which uses LP vinyl records, and an audio cassette recorder 110, which relies upon audio cassettes. Optical storage media also have been recognized as providing convenient and high quality audio play-back of music, for example. Optical storage media exclusively for sound include a digital audio tape 90 and a compact disk 10. Unfortunately, these audio systems generally do not have enough memory or capacity to store both video and audio to store movies or the like. Tapes also have not generally been used to efficiently store and retrieve information from a personal computer since tapes are extremely slow and cumbersome.
Audio and video have been recorded together for movies using a video tape or video cassette recorder, which relies upon tapes stored on cassettes. Video cassettes can be found at the local Blockbuster(trademark) store, which often have numerous different movies to be viewed and enjoyed by the user. Unfortunately, these tapes are often too slow and clumsy to store and easily retrieve computer information from a personal computer. Additional video and audio media include a laser disk 70 and a digital video disk 60, which also suffer from being read only, and cannot be easily used to record a video at the user site. Furthermore, standards for a digital video disk have not been established of the filing date of this patent application and do not seem to be readily establishable in the future.
From the above, it is desirable to have a storage media that can be used for all types of information such as audio, video, and digital data, which have features such as a high storage capacity, expandability, and quick access capabilities.
A typical storage device includes a storage media including a magnetic disk and a read/write head for reading data from the magnetic disk. In a normal, operating mode, the read/write heads are positioned above the data storage portion of the magnetic disk. More particularly, the read/write heads xe2x80x9cflyxe2x80x9d above the surface of the magnetic disk and never physically touch the data storage portion of the magnetic disk.
Upon power-down of a typical storage device, the read/write heads are typically moved from a position above the data storage portion of the magnetic disk to a safe position. This safe position is typically not above the storage portion, but at a landing region located at either the inner or outer diameter of the disk; a head load/unload ramp, often located outside the outer diameter of the disk; and the like.
If the read/write heads are not reliable moved to a safe position after power-off, the read/write heads may move around the storage device causing damage to the data storage portions of the magnetic disk resulting in data loss, causing misalignments to the read/write heads, causing damage to the read/write head elements, and causing other types of damage. The potential damage with storage devices based upon magneto-resistive (MR) read/write heads is significant due to the high cost of MR heads compared to the storage device and their more delicate nature.
Present methods for unloading of read/write heads include either maintaining the rotational speed of the magnetic disk at the same speed used for conventional operation while unloading the heads or allowing the magnetic disk to slow down at its own pace while unloading the heads. Another method includes removing a drive voltage from the spindle motor and using a Back Electro-Motive Force (back EMF, VBEMF, VEMF) voltage generated by the spindle motor to power the heads to the safe position.
One concern about relying upon present methods is that because the initial radial positions of the MR heads is unpredictable, the amount of force applied by flex cables coupled to actuator arms is unpredictable, and the load/unload ramp resistance is unpredictable. Further, because the height at which the read/write heads fly over the magnetic disk is non-linearly related to the speed of rotation of the magnetic disk, the position of the read/write heads on the load/unload ramp vary. This causes problems when loading heads onto the magnetic disk.
Another concern is that the read/write heads are not always reliably unloaded. This occurs because the amount of energy applied to the read/write heads is typically not regulated or controlled. For example, when relying upon a back EMF, where a spindle motor has a great deal of internal resistance, the spindle motor may spin-down faster than designed to do resulting in a back EMF energy that is lower than predicted. As a result of the lower back EMF energy, the read/write heads may not be reliably unloaded.
Upon power-up of a typical storage device, the read/write heads are typically moved from the safe position to a position above the data storage portion of the magnetic disk.
If the read/write heads are not carefully loaded onto the magnetic disk, the read/write heads may bounce on the magnetic disk again causing damage to the data storage portions of the magnetic disk resulting in data loss, misalignments to the read/write heads, damage to the read/write head elements, particulate generation and contamination, and other types of damage.
Concerns about present head loading methods include that the height at which the read/write heads fly over the surface of the magnetic disk is often unpredictable, thus when the heads are loaded, the heads may oscillate and touch the magnetic disk. As noted previously, because the position of the heads on the load/unload ramp vary at power-off, the speed of the magnetic disk at the moment the heads are loaded is unpredictable.
Thus what is required are methods and apparatus for providing more reliable loading and unloading of read/write heads in order to protect the read/write heads as well as the disk media.
According to the present invention, a technique including methods and a device for providing a single type of media for electronic storage applications is provided. In an exemplary embodiment, the present invention provides a methods and apparatus for unloading of MR heads from the surface of removable media.
According to an embodiment of the present invention, a method for unloading read/write heads from a surface of a magnetic disk, the magnetic disk coupled to a spindle motor includes the steps of using the spindle motor to rotate the magnetic disk at approximately a first number of revolutions per minute, positioning the read/write heads adjacent the surface of the magnetic disk, and receiving a head unload signal. The technique also includes the steps of using the spindle motor to rotate the magnetic disk at approximately a second number of revolutions per minute in response to the head unload signal, after a first predetermined amount of time after the step of receiving the head unload signal, biasing the read/write heads towards an outer edge of the magnetic disk, and after a second predetermined amount of time after the step of receiving the head unload signal, using the spindle motor to dynamically brake the magnetic disk from approximately the second number of revolutions per minute.
According to another embodiment, a method for repositioning read/write heads from a parking location to a position adjacent a surface of a magnetic disk, the magnetic disk coupled to a spindle motor, includes the steps of receiving a read/write heads load signal, and using the spindle motor to accelerate the magnetic disk typically from zero to approximately a first number of revolutions per time period, in response to the read/write heads load signal. The steps of biasing the read/write heads towards a position adjacent the surface of the magnetic disk, when the magnetic disk rotates at approximately the first number of revolutions per time period, and using the spindle motor to rotate the magnetic disk at approximately a second number of revolutions per time period, after the read/write heads are positioned adjacent the surface of the magnetic disk are also performed.
According to yet another embodiment of the present invention, a system having a storage device including read/write heads for repositioning the read/write heads from a parking location to a position adjacent a surface of a magnetic disk, the storage device includes a spindle motor coupled to the magnetic disk, for accelerating the magnetic disk to at least a first number of revolutions per time period while the read/write heads are positioned at the parking location, and a Voice Coil Motor (VCM driver) coupled to the read/write heads and to the spindle motor, for biasing the read/write heads towards the position adjacent the surface of the magnetic disk after the magnetic disk reaches the first number of revolutions per time period, wherein the spindle motor maintains a rotation of the magnetic disk at less than a second number of revolutions per time period while the read/write heads are positioned adjacent the surface of the magnetic disk, and wherein the spindle motor rotates the magnetic disk at a third number of revolutions per time period after the read/write heads are positioned adjacent the surface of the magnetic disk.
The present invention provides a more reliable method for providing the described functions. Depending upon the embodiment, the present invention provides at least one of these if not all of these benefits and others, which are further described throughout the present specification.
Further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and drawings.